(1) Field of the Invention
The present invention relates to variable camber fins for use in a moving fluid to influence that fluids flow over the fin.
(2) Description of the Prior Art
Variable camber airfoil shapes have been utilized since the beginning of aviation to achieve control of an aircraft in flight, and also to achieve an increased amount of lift on the airfoil particularly at low speeds. Such prior art airfoil shapes are shown in the following patents; Gallaudet U.S. Pat. No. 1,219,285; Stupar U.S. Pat. No. 1,220,374; and Antoni et al U.S. Pat. No. 1,317,413. All of these early airfoil designs provide external wires that are tensioned to achieve changes in the camber of a wing. However, all these control wires are provided externally to the airfoil itself. The present invention relates to a variable camber fin particularly well suited for use in an underwater environment where the control wires cannot be provided externally of the foil cross section. Such a requirement is particularly important in the environment of naval operations so as to eliminate the "noise" otherwise created by providing control wires outside a fin on a naval vessel.
Cincotta et al, U.S. Pat. No. 5,114,104, utilizes "shape memory alloy" wires adapted to be contracted an elongated selectively as a result of the application or removal of heat. The wires are provided in the skin surface of the fin itself, which skin is fabricated from an elastomeric material and therefore is readily altered in configuration so as to achieve two distinct foil shapes made possible by these "shape memory alloy" wires. The Cincotta patent is relevant to the present disclosure only insofar as the outer skin of the foil fin is fabricated from an elastomeric material.
Another prior art U.S. Pat. No. 5,150,864 issued to Roglin et al teaches an airfoil camber control system utilizing cables of "shape memory alloy". Again, the configuration for the airfoil is limited by reason of the two alternate states for the shape memory alloy wires. This patent does suggest that the shape can be varied at least spanwise of the airfoil as a result of providing segmented spanwise sections that are each capable of independent manipulation by a computer or the like. The present invention is designed to avoid the need for such complexity.
The prior art generally and the above cited references in particular fail to show or to suggest a workable system for providing the continuous control of the camber of a foil shaped fin achieved simply by altering the tension of wires strategically placed within the airfoil shape.